1. Field of the Invention
The present invention relates to a substrate arranging apparatus and method for arranging substrates, such as semiconductor wafers in a front-to-front and back-to-back arrangement.
2. Description of the Related Art
In a cleaning process carried out in connection with processes of fabricating semiconductor devices, such as an LSI circuits, various cleaning systems have been used for removing contaminants, such as particles, organic contaminants, metallic impurities and the like, from the surfaces of semiconductor wafers, i.e., substrates. The wet cleaning system has particularly prevalently been used owing to its capability of effective removal of particles adhering to wafers and of cleaning wafers in a batch processing mode.
The cleaning system has a receiving section, a cleaning section and a delivery section. The receiving section has a carrier table for receiving thereon a carrier holding, for example, twenty-five wafers, a loading mechanism for handling the carrier holding the wafers, and an arranging device for arranging, for example, fifty wafers held on two carriers transferred thereto by the loading mechanism.
In the receiving section of the cleaning system, carriers are positioned on the carrier table, and then the carriers are conveyed by, for example, a conveying device. The loading mechanism pushes up the wafers from below the carriers to take out the wafers from the carriers and carries the wafers to the arranging section. The fifty wafers thus taken out of the carriers are arranged in a row in the arranging section to wait for processing.
A wafer chuck holds collectively the wafers arranged in the arranging section and carries the same to the cleaning section. The cleaning section is provided with cleaning tanks for collectively cleaning and drying the fifty wafers. In a cleaning process, the fifty wafers arranged at predetermined intervals in parallel to each other are immersed in a cleaning liquid. In the cleaning process, the cleaning liquid, such as a sulfuric acid solution, is supplied from the bottom of the first cleaning tank so as to overflow the first cleaning tank to clean the wafers by upward currents of the cleaning liquid. The wafers thus cleaned are transferred from the first cleaning tank to the second cleaning tank. For example, a rinsing liquid is supplied to the second cleaning tank so as to overflow the second cleaning talk to rinse the wafers. The wafers thus cleaned in those cleaning tanks are conveyed to the delivery section. In the delivery section, an unloading mechanism returns the wafers to carriers, and the carriers holding the cleaned wafers are delivered from the cleaning system.
A plurality of wafers contained in the carrier are arranged in a row at predetermined intervals in parallel to each other with the front surfaces thereof directed in the same direction; that is, the front surface of one of the wafers faces the back surface of the wafer adjacent thereto. The carrier thus holding the wafers with the front surfaces of all the wafers directed toward an operating side is carried to the cleaning system by, for example, a transport robot. Consequently, it is general to clean the wafers in the cleaning tank with their front surfaces directed in the same direction.
The front surface of the wafer is mirror-furnished in a smooth surface suitable for fabricating devices thereon and the front surface is supposed to be free from particles and the like. On the other hand, the back surface of the wafer is not mirror-finished and is rough as compared with the front surface. The back surface of the wafer is contaminated with a relatively large number of particles as compared with the front surface of the same. It often occurs that particles adhering to the back surfaces of the wafers separate from the back surfaces of the wafers, move in the cleaning liquid toward the front surfaces of adjacent wafers and adhere to the front surfaces of adjacent wafers when the wafers are loaded into the cleaning tank or during a cleaning operation in the cleaning tank because, as mentioned above, the wafers are arranged with their front surfaces directed in the same direction in a back-to-front arrangement. If the front surfaces of the wafers are contaminated with particles the yield rate of products is reduced accordingly.
A cleaning method proposed to prevent the transfer of particles from the back to the front surfaces of wafers in JP-6-1 63500A cleans all the wafers collectively after rearranging the wafers in a front-to-front arrangement by a substrate arranging unit. Since the respective front surfaces of adjacent wafers face each other, particles separated from the back surfaces of the wafers will not circulate round the wafers and will not adhere to the front surfaces of the wafers, so that the reduction of the yield rate due to contamination with particles can be prevented.
A conventional cleaning system suitable for carrying out the prior art cleaning method needs a receiving unit provided with three independent mechanisms, i.e., a carrier table, a loading mechanism and a substrate arranging mechanism, to rearrange wafers in a front-to-front arrangement, in which the respective front surfaces of adjacent wafers face each other and the respective back surfaces of adjacent wafers face each other. Accordingly, the receiving section provided with those three mechanisms of the conventional cleaning system needs a large space for installation. Since the receiving section includes those three mechanisms, time for transferring wafers from the one to the next mechanism is necessary in addition to time for handling carriers on the carrier table, transporting the wafers by the loading mechanism and reversing the alternate wafers for rearrangement by the substrate arranging mechanism. When those three mechanisms need a large space for installation, processing time spent by the receiving section increases accordingly, which makes the improvement of the throughput of the cleaning system difficult.
The present invention has been made in view of those problems and it is an object of the present invention to provide a substrate arranging apparatus and method using a table, a loading mechanism and a substrate arranging mechanism, in which the loading mechanism and the substrate arranging mechanism are combined structurally to reduce the space necessary for installing the table, the loading mechanism and the substrate arranging mechanism and to reduce the time necessary for handling the wafers.
According to an aspect of the present invention, a substrate arranging apparatus comprises a table for supporting thereon a carrier holding a plurality of substrates arranged in a row in a face-to-face disposition at constant intervals, a first support mechanism capable of moving upward relative to the table through the carrier on the table to raise and support the substrates contained in the carrier, a second support mechanism capable of supporting a first group of alternate substrates among the substrates supported by the first support mechanism and of raising the substrates of the first group supported thereon relative to a second group of substrates consisting of the rest of the substrates, and rotating means for rotating one of the first support mechanism and the second support mechanism through an angle of 180xc2x0 relative to the other.
When the carrier is mounted on the table, the first support mechanism moves upward relative to the table to support a plurality of substrates contained in the carrier thereon. Then, the second support mechanism moves upward relative to the first support mechanism to support thereon the first group of substrates among those supported on the first support mechanisms. Thus, the substrates are divided in half into the second group of substrates supported on the first support mechanism and the first group of substrates supported on the second support mechanism. The first support mechanism or the second support mechanism is turned through an angle of 180xc2x0 relative to the other to reverse the substrates supported on one of the support mechanisms. Then, for example, the first support mechanism is raised relative to the second support mechanism to dispose the plurality of substrates in a front-to-front and back-to-back arrangement in which the respective front surfaces of adjacent substrates face each other and the respective back surfaces of adjacent substrates face each other.
According to another aspect of the present invention, there is provided a substrate arranging method comprising the steps of: placing a carrier holding a plurality of substrates arranged in a row in a face-to-face disposition at constant intervals; moving up a first support mechanism relative to the carrier to support the substrates in the carrier on the first support mechanism; selectively supporting a first group of alternate substrates among the substrates by a second support mechanism to cause a second group of substrates consisting of the substrates other than the substrates of the first group to remain on the first support mechanism; moving the first and second support mechanisms relative to each other to bring one of the groups of the substrates to a non-interfering position at which the one group of the substrates does not interfere with the other group of the substrates; rotating one of the second support mechanism supporting the first group of the substrates and the first support mechanism supporting, the second group of the substrates relative to each other through an angle of 180xc2x0 about a vertical axis, with the one group of the substrates at said non-interfering position; and moving the first and second support mechanisms relative to each other to combine the first group of the substrates and the second group of the substrates into a unified group of substrates arranges in a line.
According to a further aspect of the present invention, there is provided a substrate arranging method comprising the steps of: placing on a table a carrier holding a plurality of substrates; moving up a first support mechanism relative to and through the carrier on the table; supporting the substrates on the first support mechanism in a row and in a face-to-face disposition at constant intervals; selectively supporting on a second support mechanism a first group of substrates consisting of alternate substrates among the substrates supported on the first support mechanism; moving the first and second support mechanisms relative to each other to retain a second group of substrates other than the first group of the substrates on the first support mechanism and to move the first group of the substrates and the second group of the substrates to mutually non-interfering positions; rotating one of the second support mechanism supporting the first group of the substrates and the first support mechanism supporting the second group of the substrates relative to each other through an angle of 180xc2x0 about a vertical axis, with the groups of the substrates at the non-interfering positions; moving the first and second support mechanisms relative to each other to combine the first group of the substrates and the second group of the substrates into a unified group of substrates and to support the unified group of substrates on the first support mechanism in a row in a face-to-face disposition at constant intervals; and moving down the first support mechanism relative to and through the carrier on the table to retain the unified group of substrates in the carrier.
The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings.